The postmortem characteristics of Pima Indians of the Gila River Indian Community are investigated so that findings in subjects with and without diabetes mellitus can be correlated with studies in living subjects. Postmortem examinations are performed on members of the Gila River Indian Community whenever possible, regardless of whether the subjects have prior evidence of diabetes. Tissues are examined by light and electron microscopy and the histology related to the clinical findings in the same subjects. The histology of the pancreatic islets of Langerhans is being studied in detail to describe the changes that take place in diabetes. There is a significant difference between the numbers of cells of each cell type in the pancreatic islets of Langerhans in Pima infants when compared to Caucasian infants, with the Pima infants showing an excess of insulin cells and a deficit of somatostatin cells relative to Caucasians. This racial difference suggests there may be an early lesion predisposing to obesity and/or diabetes. Data have been collected for further analysis of causes of death in the Gila River Community, especially as it relates to diabetes and obesity.